Bi-modal catheter steering mechanism

ABSTRACT

Medical devices, systems, and methods for treating patients with tissue ablation include catheter systems having bi-modal steering mechanisms, which are capable of both linear and loop ablation. In other words, the catheter system may have two different steering modes: two-dimensional and three-dimensional. In the first and second steering modes, the steering actuator may cause one or more portions of the catheter shaft to bend in different planes. A steerable ablation catheter may include treatment elements such as electrodes at its distal end and along the catheter shaft, each of which may map, pace, and ablate.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of patent application Ser. No.12/546,796, filed Aug. 25, 2009, entitled BI-MODAL CATHETER STEERINGMECHANISM, the entirety of which is incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

FIELD OF THE INVENTION

The present invention relates generally to medical devices, and moreparticularly to steerable catheters, systems, and methods for treatingpatients through ablation of tissue.

BACKGROUND OF THE INVENTION

Numerous procedures involving catheters and other minimally invasivedevices may be performed to provide a wide variety of medicaltreatments, such as ablation, angioplasty, dilation and others. The term“atrial fibrillation” is a type of cardiac arrhythmia, or irregularheartbeat, in which the atria fail to contract effectively. Normal sinusrhythm of the heart begins with an electrical impulse generated by thesinus node that propagates across the right and left atria (the twosmall upper chambers of the heart) to the atrioventricular node. Atrialcontraction leads to pumping blood into the ventricles insynchronization with the electrical pulse.

During atrial fibrillation, disorganized electrical conduction in theatria causes rapid uncoordinated contractions, resulting in sub-optimalpumping of blood into the ventricle. The atrioventricular node mayreceive sporadic electrical impulses from many locations throughout theatria, instead of only from the sinus node. This electrical confusionmay overwhelm the atrioventricular node, producing an irregular andrapid heartbeat. Consequently, blood may pool in the atria and increasea risk for blood clots.

While there are numerous variations of atrial fibrillation withdifferent causes, they all involve irregularities in the transmission ofelectrical impulses through the heart. As a result, the heart does notpump the blood properly, and it may pool and clot. If a blood clot formsand moves to an artery in the brain, atrial fibrillation can lead tostroke.

The major risk factors for atrial fibrillation include age, coronaryartery disease, rheumatic heart disease, hypertension, diabetes, andthyrotoxicosis. Atrial fibrillation affects 7% of the population over 65years of age, and is also associated with increased risks of congestiveheart failure and cardiomyopathy, which warrant medical attention andtreatment. Atrial fibrillation is the most common sustained heart rhythmdisorder and increases the risk for heart disease and stroke, bothleading causes of death in the United States.

To treat cardiac arrhythmias including atrial fibrillation, physiciansoften employ specialized ablation catheters to gain access into interiorregions of the body. Such catheters often include tip electrodes orother ablating elements used to create ablation lesions thatphysiologically alter the ablated tissue without removal thereof, andthereby disrupt or block electrical pathways through the targetedtissue.

In the treatment of cardiac arrhythmias, a specific area of cardiactissue having aberrant electrically conductive pathways, such as atrialrotors, emitting or conducting erratic electrical impulses, may beinitially localized. A physician may direct a catheter through a mainvein or artery into the interior region of the heart that is to betreated. The ablating portion of the selected device is next placed nearthe targeted cardiac tissue that is to be ablated, such as a pulmonaryvein ostium or atrium.

An ablation procedure may involve creating a series of inter-connectinglesions, to electrically isolate tissue believed to be the source of anarrhythmia. During such a procedure, a physician may employ severaldifferent catheters having variations in geometry and dimensions of theablative element in order to produce the desired ablation pattern.Multiple devices having varying dimensions and shapes may also be used,to account for variations in anatomy. Each catheter may have a uniquegeometry for creating a specific lesion pattern or size, with themultiple catheters being sequentially removed and replaced to create thedesired multiple lesions.

For example, some catheters may be capable of following atwo-dimensional curve, which may be referred to as “curvilinear” or“linear” ablation. Other catheters may be capable of forming athree-dimensional shape, such as a loop that is almost transverse to thecatheter's longitudinal axis, which may be referred to as “loop”ablation.

Accordingly, it is desirable to provide a single medical device capableof both linear and loop ablation, thereby reducing the need foradditional medical devices.

SUMMARY OF THE INVENTION

The present invention advantageously provides medical devices, systems,and methods for treating patients with tissue ablation. In particular,catheter systems are provided having bi-modal steering mechanisms, whichare capable of both linear and loop ablation. The catheter system mayhave two different steering modes: two-dimensional andthree-dimensional. In the first and second steering modes, the steeringactuator may cause one or more portions of the catheter shaft to bend indifferent planes. A steerable ablation catheter may include treatmentelements such as electrodes at its distal end and along the cathetershaft, each of which may map, pace, and ablate. Optional featuresinclude a series of thermocouples for monitoring local temperatures.

Methods for ablating a tissue region are also provided, includingdirecting a treatment assembly of a medical device toward a tissueregion, and the treatment element may include a series or an array ofelectrodes; selecting a first or second steering mode; in the firststeering mode, manipulating a steering actuator from an initial positionto cause a first portion of the catheter body to bend from an initialshape to a first arc shape along a first plane; in the second steeringmode, manipulating the steering actuator from the initial position tocause the first portion to bend from the initial shape to a second arcshape, and to cause a second portion of the catheter body to bend alonga second plane; and delivering ablative energy to the treatmentassembly. The method may also include monitoring an electrical signal ofthe tissue region, such as a cardiac tissue region, or monitoringtemperatures of the electrodes.

A medical device is also provided, having a catheter body defining aproximal portion and a distal portion; a steering actuator coupled tothe proximal portion of the catheter body; a first steering elementhaving a first end attached to the steering actuator and a second endattached to the distal portion of the catheter body; a second steeringelement having a first end attached to the steering actuator and asecond end attached to the catheter body distal to the first steeringelement; and an electrode array disposed on the distal end of thecatheter body. The first steering element may be attached to a firstside of the distal portion, and the second steering actuator may beattached to a second side opposite the first side of the distal portion,such that manipulation of the steering actuator in a first directiontensions the first steering element to deflect a portion of the catheterbody in a first direction in a first plane and manipulation of thesteering actuator in a second direction tensions the second steeringelement to deflect a portion of the catheter body in a second directionin a first plane. The catheter body may include a first deflectablesegment proximal to the electrode array, the first deflectable segmentbeing biased to deflect in a plane substantially perpendicular to thefirst plane. A stiffener element may be slidably disposed within thecatheter body and slidably positionable within the first deflectablesegment. The medical device may include a first anchoring elementcircumscribing the catheter body where the first steering elementattaches to the distal portion; and a second anchoring elementcircumscribing the catheter body where the second steering elementattaches to the distal portion.

A medical device having a catheter body; a guide member within thecatheter body, the guide member defining a first segment having a firstplane of preferential bending, and a second segment having a secondplane of preferential bending substantially perpendicular to the firstplane; a first steering element having a first end attached to the firstsegment of the guide member; a second steering element having a firstend attached to the second segment of the guide member; and an electrodearray disposed on the distal end of the catheter body is also provided,and may also include a first steering actuator coupled to the firststeering element, and a second steering actuator coupled to the secondsteering element, where manipulation of the first steering actuatortensions the first steering element to deflect a portion of the catheterbody in the first plane, and wherein manipulation of the second steeringactuator tensions the second steering element to deflect a portion ofthe catheter body in the second plane.

A more complete understanding of the present invention, and itsassociated advantages and features, will be more readily understood byreference to the following description and claims, when considered inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In this description, reference will be made to the attached drawings:

FIG. 1 is a side elevation view of a first catheter embodiment;

FIG. 2 is a partial cross-section view of the catheter shaft of FIG. 1,showing different steering modes;

FIGS. 2A-2C are partial perspective views of a catheter, showing loopsteering;

FIG. 3 is a partial cut-away view of a catheter, showing loop steering;

FIGS. 4 and 5 are partial perspective views of a guide plate;

FIGS. 6 and 7 are partial perspective views of additional guide plates;

FIG. 8 is a side elevation view of a second catheter embodiment;

FIGS. 9 and 10 are partial views, showing different positions of astiffening wire;

FIGS. 11A-12C are partial cross-section views of the catheter of FIG. 8,showing different steering modes;

FIGS. 13A and 13B are partial cross-section views of the catheter shaftof FIG. 8;

FIGS. 14A-15 are partial views of catheters, showing loop steering;

FIGS. 16 and 17 are side elevation views of a third and fourth catheterembodiment;

FIGS. 18 and 19 are partially diagrammatic views of catheters havingthermocouples; and

FIG. 20 is a partial view some catheter components.

DETAILED DESCRIPTION OF THE INVENTION

The present invention advantageously provides medical devices, systems,and methods for treating patients, in particular with catheter systemshaving bi-modal steering mechanisms, which are capable of both linearand loop ablation.

Referring to the drawings, the present invention provides variousembodiments of medical devices for treating patients, which may be inthe form of catheters having more than one steering mode. Theillustrations of course depict only some of many different possiblecatheter designs that are within the scope of the present invention. Forclarity and convenience, the present detailed description will onlydescribe a few embodiments.

The catheters of the present invention may be sized and dimensioned forintraluminal and transseptal access to a patient's heart for thetreatment or ablation thereof. Some of these embodiments are in the formof catheters generally designated at reference numerals 10 and 12, andcatheter shaft designs generally designated at reference numerals 14 and16.

A first example embodiment of the present invention is shown in FIG. 1.Medical device 10 may generally define an elongated, flexible catheterbody 18 with proximal and distal ends having a distal treatment assembly20 that may include a series of electrodes 22, as well as a handleassembly 24 at a proximal end or portion of the catheter body 18. Thecatheter body 18 may be formed and dimensioned to provide sufficientcolumn and torsional strength to support standard interventionalprocedures such as those which access the vasculature from a femoralvein or artery and further access the patient's heart. The cathetershaft may include reinforcement elements or otherwise be constructed toprovide desired degrees of stiffness, flexibility, and torquetransmission along the length of the body and at selected locationsalong its length. For example, the catheter body may have portions orcomponents of differing size, thickness or flexibility, and may includewires, braiding, changes in wall thickness, additional wall layers orcatheter body components, sleeves, or other components reinforcing orotherwise supplementing an outer wall or thickness along its length.Some portions that may experience significant loading or torque during aparticular procedure may also include reinforcement.

FIG. 1 depicts medical device 10 having a handle assembly 24 with a knobor steering actuator 28. Steering actuator 28 may have an initial orneutral position, and may be moved in one direction to a first position,and in another direction to a second position. The catheter shaft mayhave portions of relatively higher and lower flexibility, and may have aproximal portion of a larger size than a distal portion.

The catheter shaft design of this first example embodiment is shown inFIG. 2. A first and second steering member or wire 34 and 36 aredepicted, affixed to radially or diametrically opposite sides of thecatheter body 18. First and second steering wires 34 and 36 haveproximal ends coupled to steering actuator 28 for selectively pullingeither steering wire. The steering wires 34 and 36 are generally freefrom attachment to other catheter components up to a first and secondattachment point 38 and 40, which are at different longitudinalpositions. These different attachment points enable the same steeringactuator 28 to select and operate the catheter in a first steering modeby twisting or moving steering actuator 28 in a first direction, and toselect and operate the catheter in a second steering mode by twisting ormoving steering actuator 28 in a second direction. Accordingly, a singlesteering actuator 28 can provide two different steering modes, eithertwo-dimensional or three-dimensional.

The catheter body may also have at least four portions of alternatinghigher and lower flexibility 52, 54, 56 and 58. The distal portion ofhigher flexibility 52 may encompass the treatment assembly 20, forexample including all of the electrodes 22, and this portion may be whatbends to form the curved shape of the two-dimensional steering mode, andto form the loop of the three-dimensional steering mode. The proximalportion of higher flexibility 56 may encompass bending in thethree-dimensional steering mode, to create the desired angle of the loopwith respect to the longitudinal axis. In a specific example, theportions of higher flexibility may be polymers having durometers of30-40 D, and the portions of lower flexibility may be polymers havingdurometers of 50-60 D.

The catheters of the present invention may have a proximal and distalplane of preferential bending. This compound preferential bending may beachieved with a guide plate 64 as shown in FIGS. 3-5, having proximaland distal portions 66 and 68 and a transition portion 70. Transitionportion 70 may have the illustrated twisted shape, and the angle may beselected as desired, which may for example be 90 degrees. The proximalportion 66 of guide plate may optionally have a curved or concavesection 71, which may be provided to bias the catheter shaft during thethree-dimensional steering mode. Additional possible designs for guideplates are shown in FIGS. 6 and 7.

In operation, the steering actuator 28 may initially be in a neutralposition, and the distal catheter shaft will be generally straight (withthe possible exception of a curved or concave section 71 of a guideplate), though it will of course tend to follow the shape of any bodypassage or lumen. FIG. 1 illustrates the treatment assembly 20 asgenerally following an x-axis. For linear ablation, or at any timetwo-dimensional steering is desired according to the first steeringmode, the steering actuator 28 may be moved or rotated in a firstdirection to a first position, thus pulling on first steering member 34and causing distal portion 68 of guide plate 64 inside the catheterbody's distal portion of higher flexibility 52 to bend in the distalplane of preferential bending. This bending may be toward the y-axis ofFIG. 1, into a shape illustrated in FIG. 2A. In the two-dimensionalsteering mode, the term “linear” of course includes curving lines, asshown in FIG. 2A.

For loop ablation, or at any time three-dimensional steering is desiredaccording to the second steering mode, the steering actuator 28 may bemoved or rotated in a second direction to a second position, thuspulling on second steering member 36. In this second steering mode,distal portion 68 of guide plate 64 inside the catheter body's distalportion of higher flexibility 52 will bend in the distal plane ofpreferential bending, but in the opposite direction as illustrated inFIGS. 2B and 2C. Simultaneously, proximal portion 66 of guide plate 64inside the catheter body's proximal portion of higher flexibility 56will bend in the proximal plane of preferential bending.

In this three-dimensional steering mode, a distal portion of catheterbody may be formed into a loop as shown in FIGS. 2B and 2C, and a moreproximal portion of catheter body may bend toward the z-axis of FIG. 1,such that the loop defines an angle with respect to the longitudinalaxis of an adjacent portion of catheter body. This angle may havewhatever magnitude the physician prefers, including 90 degrees. An anglesomewhat less than perpendicular may be selected, to provide a measureof resilience or tactile feedback when contacting tissue.

Another example embodiment of a medical device according to the presentinvention is shown in FIG. 8, having a bi-directional shaft design witha discrete mechanism for selecting between different steering modes.Catheter 12 is generally similar to catheter 10 with a handle assembly26 having a steering knob or actuator 30 as well as an additionalcontroller, such as for example slider 32, and a different cathetershaft design 16.

This mechanism for selecting different steering modes may be in the formof a movable stiffener 48, shown in FIGS. 9-12C. The stiffener 48 may bemoved to the distal position of FIGS. 9 and 11A-11C, selecting a firstmode of steering, or to the proximal position of FIGS. 10 and 12A-12C,thus selecting a second steering mode. In the first steering mode ofFIGS. 9 and 11A-11C, stiffener 48 may oppose bending of the proximalportion 66 of the guide plate 64, which may be referred to astwo-dimensional or “linear” steering. On the other hand, in the secondsteering mode of FIGS. 10 and 12A-12C, stiffener 48 is retractedproximally and allows bending of the proximal portion 66 of the guideplate 64 (toward the z-axis for example), which may be referred to asthree-dimensional or “loop” steering.

The catheter shaft design of this second example embodiment is shown inFIGS. 13A and 13B, depicting another pair of first and second steeringwires 42 and 44, affixed to radially or diametrically opposite sides ofthe catheter body at the same longitudinal position 46. First and secondsteering wires 42 and 44 have proximal ends coupled to steering knob 30for selectively pulling either steering wire. The steering wires 42 and44 are generally free from attachment to other catheter components up toattachment points 46. With both of the steering wires 42 and 44 actingon the same longitudinal position, the steering actuator 30 is operableto bend the catheter shaft in a first and second direction by twistingor moving the steering actuator in a first and second direction,respectively, in both a first and second steering mode.

In embodiments having the bi-directional shaft design, the stiffener 48is coupled at its proximal end with a controller, such as for exampleslider 32 shown in FIG. 8, which is operable to move stiffener betweenthe distal position of FIGS. 9 and 11A-11C and the proximal position ofFIGS. 10 and 12A-12C. This bi-directional shaft design also allowshybrid steering modes: by moving the stiffener 48 to intermediatepositions between the proximal and distal positions, combinations of thefirst and second steering modes may be achieved.

Additional optional components for catheter shafts according to thepresent invention may include reinforcements such as for example a braidor coil embedded in or affixed to the catheter body, which may be madeof any suitable material including metals and strong polymers. Specificexamples of reinforcing materials may include stainless steel andnitinol. These reinforcing components may also be used to more stronglyaffix the steering wires to the catheter body, such as for example byembedding them into the wall of catheter body, inside or outside of (oreven woven among) reinforcing components. FIG. 15 also illustratesoptional anchoring components, which may include a first and secondanchoring ring 60 and 62, and which may be used to affix the steeringwires to the catheter body.

Another example embodiment of a medical device according to the presentinvention is shown in FIG. 16, having a supplemental steering mechanismfor more agile manipulation of the distal assembly. Catheter 76 has ahandle assembly 78 having a first and second steering knob or actuator80 and 82. First steering actuator 80 may be generally similar tosteering actuator 28 of catheter 10, or may be generally similar tosteering actuator 30 of catheter 12 with the addition of optional slider84 for controlling a stiffener.

Second steering actuator 82 may be used to bend and steer a moreproximal portion of the catheter shaft, to more deftly position thedistal assembly near a desired site of tissue for treatment. In cathetershaft designs having at least four alternating portions of higher andlower flexibility, the second steering actuator 82 may enable bendingand steering of a supplemental steering portion, which is proximal ofthe proximal portion of higher flexibility.

Another example embodiment of a medical device according to the presentinvention is shown in FIG. 17, having a supplemental steering mechanismin the form of a steerable catheter sheath 86, which at least partiallysurrounds an ablation catheter 88 according to the present invention.Catheter 88 has a handle assembly 90 having a steering knob or actuator92, and may have an optional slider 94. Catheter sheath 86 has a handleassembly 96 with a sheath steering knob or actuator 98. Catheter 88 andcatheter sheath 86 may be moved, more specifically advanced, retractedor rotated, with respect to each other. The sheath steering actuator 98may be used to bend and steer a selected portion of the catheter shaft,and sheath 86 may be moved so as to steer different portions of thecatheter shaft.

Now referring to FIGS. 18 and 19, the distal treatment assembly 20provides for the treatment, monitoring, or otherwise clinicallyinteracting with a desired tissue region, such as the heart. Thetreatment assembly 20 may include, for example, an array or series ofelectrodes 22 disposed near, on, or substantially on the distal end ofthe catheter body. The electrodes 22 may be mounted to detect electricalsignals between any pair of electrodes (bi-pole) for mapping ofelectrical activity, and/or for performing other functions such aspacing of the heart. Moreover, the electrodes 22 may deliver ablationenergy across an electrode pair or from independent electrodes whendelivering monopolar energy. In a particular example, the plurality ofelectrodes may include from eight to twelve electrodes, with eithersymmetric or asymmetric spacing. The electrodes 22 may be constructedfrom platinum, iridium, or any other suitable material.

Each electrode 22 may include a temperature sensor or thermocouple 72located on or near the tissue side of the electrode, to monitor thetemperature at each ablation site before and during ablation. Indeed,each electrode 28 may have a pair of thermocouples at radially ordiametrically opposite points. The thermocouples are electricallyconnected to the handle assembly by conduits or wires, which mayoptionally be at least partially surrounded by a coil 74 shown in FIG.20 to improve signal fidelity. To reduce the quantity of thermocouplesand associated wires, a smaller number of thermocouples may be used andarranged specifically to still provide good performance. For example, aquantity of the temperature sensors is at least equal to a quantity ofthe electrodes, and is at most twice the quantity of electrodes. A moredetailed example includes at least eight electrodes, and at most twelvetemperature sensors. In the specific examples depicted in FIGS. 18 and19, ten electrodes and twelve thermocouples are depicted. Thethermocouples shown in FIG. 18 are arranged generally on one radial sideof the catheter body, with two thermocouples on the radially oppositeside of the catheter body. In FIG. 19, the thermocouples are positionedon alternating radially opposite sides of the catheter body.

It should be understood that an unlimited number of configurations forthe present invention could be realized. The foregoing discussiondescribes merely exemplary embodiments illustrating the principles ofthe present invention, the scope of which is recited in the followingclaims. In addition, unless otherwise stated, all of the accompanyingdrawings are not to scale. Those skilled in the art will readilyrecognize from the description, claims, and drawings that numerouschanges and modifications can be made without departing from the spiritand scope of the invention.

What is claimed is:
 1. A medical device, comprising: a catheter bodydefining a proximal portion and a distal portion, the distal portionincluding a plurality of adjacent segments having alternating relativeflexibilities, the plurality of adjacent segments having alternatingrelative flexibilities including a first segment, a second segmentimmediately proximal to the first segment, a third segment immediatelyproximal to the second segment, and a fourth segment immediatelyproximal to the third segment, the first and third segments being moreflexible than the second and fourth segments; a guide member within thecatheter body, the guide member defining a first outer edge, a secondouter edge, a longitudinal axis, a width that is perpendicular to thelongitudinal axis and extends directly from the first outer edge of theguide member directly to the second outer edge of the guide member, alength that is located along the longitudinal axis, a first segmenthaving a first plane of preferential bending, a second segment having asecond plane of preferential bending substantially perpendicular to thefirst plane of preferential bending, and a transition portion betweenthe first segment and the second segment, the first segment having adistal section, a proximal section, and a middle section locateddirectly between the distal section and the proximal section, the middlesection having a width that extends directly from the first outer edgeof the guide member directly to the second outer edge of the guidemember, the distal section and the proximal section being linear andlocated along the longitudinal axis of the guide member and an entiretyof the middle section having an arc of curvature when the guide memberis in an at least substantially linear configuration, the second segmentof the guide member being within the first segment of the catheter bodyand the first segment of the guide member being within the third segmentof the catheter body; a steering actuator coupled to the proximalportion of the catheter body; a first steering element having a firstend attached to the steering actuator and a second end attached to thedistal portion of the catheter body at a first position; a secondsteering element having a first end attached to the steering actuatorand a second end attached to the catheter body at a second positiondistal to the first position; and an electrode array disposed on thefirst segment of the distal portion of the catheter body.
 2. The medicaldevice according to claim 1, wherein the first steering element isattached to a first side of the distal portion, and the second steeringelement is attached to a second side of the distal portion opposite thefirst side of the distal portion.
 3. The medical device according toclaim 1, wherein manipulation of the steering actuator in a firstdirection is configured to tension the first steering element to deflecta portion of the catheter body in a first direction in a first plane. 4.The medical device according to claim 3, wherein manipulation of thesteering actuator in a second direction is configured to tension thesecond steering element to deflect a portion of the catheter body in asecond direction in a second plane.
 5. The medical device according toclaim 4, wherein the the middle section of the first segment of theguide member is biased to deflect the third segment of the catheter bodyin a plane substantially perpendicular to the first plane.
 6. Themedical device according to claim 1, further comprising a firstanchoring element at the first position; and a second anchoring elementat the second position.
 7. The medical device according to claim 1,wherein each electrode of the electrode array includes at least onetemperature sensor.
 8. The medical device according to claim 1, whereinthe first and second steering elements are steering wires.